Occipitocervical fixation may be accomplished by using a bone plate attached to the occiput bone on the posterior of the skull, in conjunction with spinal rods. In many cases, the bone plate is attached to the skull with bone screws. Drilling and tapping holes at the rear of the skull is a difficult procedure that requires a significant amount of force to penetrate the dense cortical bone. The process is further complicated by the angle of approach that is required for instruments. Because the plate is positioned in close proximity to the back of the neck, the working area around the plate location is extremely confined. Moreover, the orientation of the plate is such that the plate extends more or less normal to the axis of the cervical spine. Typical bone plates feature holes with axes that extend normally to the surface of the plate. In this arrangement, the axes of the screw holes are very close to the axis of the cervical spine. Consequently, the surgeon must position screw drivers, drills and taps right up against the cervical spine to maintain the proper trajectory while drilling and tapping the occiput bone, and driving bone screws through the plate.
Conventional screw drivers, drills and taps have relatively long shafts. To position these instruments so as to achieve the proper trajectories, the shafts must be positioned normal to the plate, right up against the cervical spine. Therefore, the surgeon must make a long incision along the axis of the cervical spine to make room to maneuver the instrument shafts. Large incisions are clearly undesirable because they are invasive, introduce greater risk of complications, and require long recovery times. Moreover, longer incisions are not always effective in providing sufficient clearance for instruments. Cervical deformities that obstruct the area around the occiput bone, for example, can make it impossible to position instrument shafts at the proper angle necessary to access the screws.
For the foregoing reasons, conventional occipitocervical fixation implants and techniques have many unresolved drawbacks.